A side feeder is frequently used when adding in particular powdery substances in the extruder. Such a device is frequently used in the extrusion process for the lateral charging of the main extruder and assists the manufacture of high-quality products. The material throughput is increasing continuously in modern extrusion systems so that the product quantities, in particular the additives which must be fed to the extruder system are becoming increasingly greater. It has proved to be disadvantageous that gaseous concomitant materials such as, for example, intermediate air are conveyed in the pores of the material and in particular in powdery substances. However, the gaseous concomitant materials cannot flow into the conveyor screw of the extruder system since they cannot be transported via completely filled zones in the conveyor screw. Practice shows that the gaseous concomitant materials flow back into the feed housing, in particular into the feed hopper and counteract the inflow of material to be conveyed, which can have a negative influence on the supplied quantity of material.
A screw machine for the treatment of at least partially powdery material is deduced from EP 2 218 568B 1. The machine comprises a housing with a feed opening which is disposed at one end of the housing and which is used for feeding material. Furthermore, at least one conveyor screw is provided in a housing bore. In addition, a metering device is provided which is located upstream of the feed opening and which is used for feeding material. In addition, a vacuum housing section is provided which is configured detachably in the housing. The vacuum housing section is a filter unit in the form of a metal nonwoven which is held exchangeably as a gas-permeable wall section on a base body.